1. Field of the Invention
The present invention relates generally to grinding machines, and more particularly to a cam grinding machine for grinding automotive cams and the like.
2. Description of the Prior Art
In conventional cam grinding machines for grinding a cam supported on a work spindle with a grinding wheel while rocking the work spindle on the traces of the profile of a master cam, the rotational speed of the work spindle is reduced at the same time as the infeed movement of the grinding wheel is stopped, in order to finely finish the ground surface of the cam. Such rotational control of the work spindle, however, causes the cam to return to its ideal rotational axis as quickly as a spring, and thus, a part of the cam, which was to be ground during the last rotation before the speed reduction, but is left unground, is subsequently ground in the condition of the work spindle being rotated at the slow speed, whereby cracks are created upon this part of the cam because it receives heating and cooling for an extremely short period of time due to the fact that the decrease of the relative circumferential speed between the cam and the grinding wheel lowers the metal removing ability of the grinding wheel. Especially, it is a serious problem that cracks and the heat-affected surface layer created upon the top or sloping-up profile portion of the cam are left unremoved, irrespective of the performance of the fine grinding operation.